The invention relates generally to magnetoresistive recording heads for hard disk drives. More specifically, the invention relates to methods and devices for determining the operational and structural integrity of magnetoresistive recording heads.
The surface quality of the air-bearing surface, including the reader-to-shield isolation, of a magnetoresistive recording head is of extreme importance to the performance of the head as well as to its projected life expectancy. With recent advances in magnetic data storage, the reader gap thickness in magnetoresistive read/write heads has decreased significantly. This increasingly smaller gap has created a situation where the application of as little as a one or two volt potential difference across the reader and one or more neighboring shields can irreparably damage the recording device.
Currently, there is no fast, accurate method to determine the quality of the finished surface of a recording head that is intended to be used in a hard disk drive. One known method is to obtain electron micrographs of the finished surface. The acquisition of electron micrographs is time consuming and may destroy the head. Further, micrographs do not always provide an accurate representation of the degree of electrical isolation. Hand-probing individual sliders to verify that the isolation is intact can also cause severe damage to the head so that it is no longer useful for a drive. Hand-probing has also become increasingly difficult to perform as the dimensions of the shields have decreased. Both of these currently utilized methods guarantee only partial sampling because of the amount of time required for each test, and the destructive nature of the tests.
Other exemplary methods for finishing recording heads and evaluating integrity include both of Mowry et al., U.S. Pat. Nos. 5,463,805 and 5,559,429, which disclose systems for lapping magnetoresistive sensors. The Mowry et al. processes include simultaneous lapping of a lap monitor and the magnetoresistive sensor to provide the desired resistance. The resistance of the magnetoresistive sensor is set by comparison to a reference resistor in order to provide the target resistance. Chang et al., U.S. Pat. No. 4,912,883 also discloses a lapping control system for thin film magnetic transducers. The Chang et al. system uses the correlation between saturation current and transducer throat height to regulate the termination of lapping. Keel et al., U.S. Pat. No. 5,402,074 discloses an apparatus and process for measuring core-to-coil impedance and integrity of a recording head. The structure of Keel is limited to measurements at wafer level, and cannot be used for measurement at other stages of processing and functioning.
Other methods are also available for evaluating the integrity of head components. For example, Shultz, U.S. Pat. No. 5,390,420 discloses a device and process for determining the alignment between magnetoresistive elements and contacts. Further, Shultz et al., U.S. Pat. No. 5,514,953 discloses a process for measuring differences in magnetic domains among multiple magnetoresistive sensors.
However, even with these processes and devices, there still remains a need for a device and method for measuring the electrical isolation of a magnetic recording head that is nondestructive and that can be used at any point throughout fabrication, testing and use of a magnetoresistive recording head.
In accordance with one aspect of the invention there is provided a magnetoresistive recording head including a reader portion having at least one shield, at least one reader contact, that is electrically connected to the reader portion, a shield shunt, at least one auxiliary electrical connection, and at least one auxiliary electrical contact that is electrically connected to at least one of the shields.
In accordance with another aspect of the invention there is provided a magnetoresistive recording head including the reader portion that has a top and bottom shield, a first auxiliary electrical connection, a second auxiliary electrical connection, a first auxiliary electrical contact, and a second auxiliary electrical contact, where the first auxiliary electrical connection electrically connects the first auxiliary electrical contact to the top shield, and where the second auxiliary electrical connection electrically connects the second auxiliary electrical contact to the bottom shield.
In accordance with yet another aspect of the invention there is provided a method of determining the electrical integrity of a magnetoresistive recording head that includes fabricating a magnetoresistive recording head including a reader portion having at least one shield, at least one reader contact, that is electrically connected to the reader portion, a shield shunt, at least one auxiliary electrical connection, and at least one auxiliary electrical contact that is electrically connected to at least one of the shields, and measuring the integrity of the magnetoresistive recording head.
A device and method of determining reader-to-shield isolation and the surface quality of a fully functional magnetoresistive recording head are provided. This improvement to the design of a traditional recording head offers the ability to measure the reader-to-shield isolation, capacitance, leakage current, and break-down voltage across the reader gap. The evaluation may be done at wafer-level, slider-level, or HGA-level under the same geometrical conditions as an actual recording head.
Furthermore, the improved head can be used to test, quantify, and improve the lapping process of recording heads in the slider portion of the process. This differs from known methods of using a lap monitor to determine device integrity during the lapping process.